Protesters threw cans, rocks and bottles at the officers, who police used batons to push away the angry mob, footage broadcast by the 24 Horas news channel showed.
Thousands of others gathered in the regional capital’s major avenue for a peaceful demonstration. They threw toilet paper rolls in the air as a sign that "much needs to be cleaned up" in the region.
Calls have been mounting for the Catalan interior chief, Miquel Buch, to resign after he condemned protesters and defended police actions.
Protests began on Monday after the top Spanish court in Madrid gave prison terms ranging from nine to 13 years to nine former Catalan leaders on sedition charges for their role in organizing the 2017 independence vote.